Cap for a writing instrument



FIG. 1 is a front elevational view of a cap for a writing instrument according to the present;

FIG. 2 is a rear elevational view of FIG. 1;

FIG. 3 is a right side elevational view of FIG. 1;

FIG. 4 is a top plan view of FIG. 1;

FIG. 5 is a bottom plan view of FIG. 1; and,

FIG. 6 is a front perspective view of FIG. 1. 

The ornamental design for a cap for a writing instrument, as shown and described. 